There is a direct correlation between velocities and pressures - BUT . . . the only criteria for demonstrating this is to use the exact same loading techniques, bullet, primer, crimp, and brass, and as you increase the volume of the same powder, you will see a direct linear increase in pressure and velocity. Change any of these variables and there is no way to gauge the pressure effects by velocities alone. Random experimentation will result in having no idea of what pressures you are working with, so stick with the reloading manuals, since those loads have been pressure tested.

A great example is to think about proof testing by arms manufacturers. Shotgun companies often test with a 2X max-pressure proof load and the shotgun shell looks exactly like any low pressure target round.

I do not think there are any 100% reliable ways to visually determine over-pressure loads without physically measuring it as you shoot. Hardly anyone has the equipment or capability to do that.

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Gary
SWCA 2515